Linked JS files are transpiled before prepending/appending

[realfish]

Quick summary:

It seems that the linked JS files are transpiled (by Babel) before they are concatenated. This kind of processing may introduce errors due to Babel locally/partially transforming code snippets.

Expected behaviour:

Do JS transpiling only after all linked files are concatenated.

A sample that shows the issue:

Please check realfish/codekit3-issue329 out.

In the repo,

• 'test/app1.js' is transpiled from 'src/_app1.js', which is the entry (master file) of 'foo.js', 'bar1.js' , and 'bar2.js'.
• 'test/app2.js' is transpiled from 'src/_app2.js'.

The source codes without transpiling of '_app1.js' (concatenated) and '_app2.js' should be identical. After processing however, there is at least one critical difference between 'test/app1.js' and 'test/app2.js' as follows.

Notice the re-declared variable _templateObject in 'app1.js', which is introduced by some ES2015 transformations via Babel. (The re-declaration is an error.) Meanwhile in 'app2.js', the seperate _templateObject and _templateObject2 variables are the expected transformation.

[realfish]

Oops, may be a duplication of #136.